/**
 * Copyright (C) 2008 GeoScheduler Team, as stated on <http://www.geoscheduler.org/authors>.
 * 
 * This file is part of GeoScheduler.
 * 
 * GeoScheduler is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * GeoScheduler is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with GeoScheduler. If not, see <http://www.gnu.org/licenses/>.
 */

package org.geoscheduler.commons.collections;

import java.util.Iterator;

/**
 * 
 * <h2>CompoundIterator</h2>
 * <p>
 * Helper class providing {@link Iterator} behaving as facade for group of
 * iterators. Control is transfered to next iterator, when first one
 * {@link #hasNext()} method returns <code>false</code>.
 * </p>
 * 
 * @author LKo (Lukas.Kolisko@Geoscheduler.Org)
 */
public class CompoundIterator<T> implements Iterator<T> {

	private Iterator<T> active;
	private final Iterator<Iterator<T>> inners;

	public CompoundIterator(Iterator<Iterator<T>> inners) {
		this.inners = inners;
	}

	public boolean hasNext() {
		while (active == null || (!active.hasNext() && inners.hasNext())) {
			active = inners.next();
		}
		return active == null ? false : active.hasNext();
	}

	public T next() {
		return active.next();
	}

	public void remove() {
		throw new UnsupportedOperationException("Read only compound iterator");
	}
}
